This invention is a method used to produce various interference filters with only one single material in vacuum conditions. It can be applied to photo-electronic displaying, optical fiber communication, optical measure systems, energy control, to interferometer, military weapons, etc.
1. Background of the invention
Optical coating is an indispensable technique for optical systems. For example, the sensitivity of photo-electronic signals will be improved when going through optical coating. And most of the films designed for these components are multilayer interference thin films composed of two or more kinds of materials at present. However, the production of these films is more difficult due to complex refractive indices of different materials. To solve this problem, two materials, with high and low refractive index each, are mixed by co-evaporation to produce a special thin film whose refractive index falls between the original two. Although the interference effect of multilayer films is improved, its production is difficult and inconvenient to control, and the stability of the optical multilayer interference films is poor.
Currently optical thin films, often called as optical interference filters, are mostly used in treatment of optical signals and change of light properties to satisfy requirements of experiments. In spite of theoretical design availability, two or three, even more, layers of materials with different refractive indices must be used to reach the required optical effect. Due to the unique properties of each material, different coating method has to be adopted and thus the difficulty of production is greatly increased.
1. Description of the Prior Art
Lee Cheng-Chung et al, on xe2x80x9cInterference coating based on the synthesis of silicon nitridexe2x80x9d in Applied Optics (vol. 38, no. 1, pp. 2078-2082, 1999), disclosed that, under the conditions of using ion beam composed of N2+ mixed with Ar+, Si could be made into SiNx whose refractive index changed from 3.5 to 1.72 at a wave length of 1550 nm. According to the above-said conditions, broadband pass filters, narrowband pass filters, and antireflection films could be produced and applied in optical fiber communication, laser interference devices, optical measure systems, energy control and military weapons.
The Invention uses only one single material to coat various optical thin films with different refractive indices in vacuum conditions. Multilayer filters with different refractive indices can be made at one time, with no need to replace materials in the production process. All you need to do is to change the contents of the gas in the high vacuum coating chamber. Since the production process of the Invention is pretty simple, coating machines adopting the method can be compact in design and easy to operate. Besides, the cleaning and maintenance of their coating chambers can be done easily and conveniently.
One who is familiar with the similar techniques can clearly understand the purposes and features of the invention by the illustration of the examples listed below.